Accuracy of Renal Stone Classification by Dual-Energy Computed Tomography

Abstract

This study aimed to evaluate the diagnostic accuracy of dual-energy computed tomography (DECT) in classifying renal stone composition compared with radiologist interpretation as the reference standard, and to identify factors associated with diagnostic accuracy. Methods: This retrospective cross-sectional study included patients who underwent non-contrast CT of the kidneys, ureters, and bladder (CT KUB) using a low-dose DECT kidney stone protocol at Rajavithi Hospital between October 1, 2021, and September 30, 2024. A total of 75 patients with 171 renal stones were analyzed. Stone characteristics, including attenuation values (Hounsfield units), volume, maximum diameter, and dual-energy index (DEI), were measured. Stone classification obtained from DECT was compared with radiologist interpretation using the Chi-square test and Fisher’s exact test. The CT system underwent routine quality control according to manufacturer and radiology standards, including assessment with a CT quality control phantom to verify CT number accuracy, image uniformity, contrast resolution, and slice thickness. Standardized acquisition and post-processing protocols were applied throughout the study to minimize measurement variability.

The results revealed that DECT demonstrated high diagnostic accuracy for renal stone classification, particularly in differentiating uric acid stones from calcium-containing stones. The diagnostic performance showed an accuracy of 97.13%, sensitivity of 98.43%, specificity of 93.18%, positive predictive value of 97.66%, and negative predictive value of 95.35%. DECT-based classification was in significant agreement with radiologist interpretation (p < 0.001).

DECT is a reliable and effective imaging modality for renal stone characterization and can support clinical decision-making and treatment planning in patients with nephrolithiasis.